Scientists have figured out how it is that some petunia plants veer away from violet and red, and instead bloom in bursts of a rare shade of blue. The cause, they have found, is a faulty protein that produces petals that are too alkaline. Petunias typically sport red or violet petals, which are highly attractive to pollinating insects. Occasionally a blue mutant will crop up, a color which is less attractive to pollinating insects. Researchers knew that acidity in the petals affected their coloration, but now they have discovered that the variation is tied to the function of a single kind of cellular pump. The newly found pump hyperacidifies petunia petals by pumping protons into petal compartments, making petals much more acidic than the rest of the plant. Those protons interact with pigments in the petal, called anthocyanins, to produce the petal's color. When the pump is working, the petal is acidic, and the color is reddish. When it's faulty, and the petals aren't super-acidic, the color is blue.
Petunia petal pH
The team identified the genes that make up the cellular pump and found that a mutation in just one of the genes could result in blue petals. "By studying the difference between blue and red flowers of petunias, we have discovered a novel type of transporter able to strongly acidify the inside of the vacuole," says study author Francesca Quattrocchio of VU-University in Amsterdam. Scientists may be able to expand their discovery of this cellular pump and its role in vacuole acidity to help generate new colors in flowers or new tastes in fruits, she says. The work is published today in Cell Reports. Image by Leonora Enking via Flickr